Process for hardening artificial stone.



' nnrr sitar PROGEfiS F 011 EABDENTNG BLRTIZFIGIAL STONE.

Specification of Letters Patent.

Patented April 28, 12908.

Application filed December 4, recs. Serial Ho. sies a.

To all whom it may concern.

Be it known that we, Enron 'S-onwANnN- Buns, a subject of'the King of Prussia, re-' siding at Hanover, Germany, and ALBERT Burns, a subject of the Kingof Prussia, 1'97 siding at Hanover, Germany, have invented certain new and useful 'im roveinents in.

recesses for'hardening arti cial stones of hydrate of lime and filling substances by means of carbonic acid or gases containing carbonic acid, of which thefollowing is a specification.

-Numerous processes have already been proposed for hardening artificial stone con-- taining hydrate of lime, by means of can bonic acid or gases containing the same. Thus, it has been proposed to treat the artificial blocks with carbonic acid at ordinary temperature under gradually increasing pressure, in suchmanner that a constant temperature of 32 C. is roduced and maintained in order to obtain a thorough action of the carbonic acid. It has also been proposed to use carbonic acid of very high percentage in order to eflect a very rapid hardening and drying of the block. Of these processes the first is undesirable because it necessitates iery strong vessels arid the blocks must-.be dried beforehand; this process seems to necessitate also the employment of carbonic acid of high percentage The second process not only necessitates the use of carbonic acid of very high percentage, but is undesirable for the further reason that the temperature produced by the combination of the carbonic acid with the lime falls rapidly by reason of the fact the reaction is greatly abated in consequence of the newly-formed calcium-carbonate surrounding the hydrate of lime. Thus a suiiicient evaporation of the resultant moisture in the blocks does not take place, and a thorough and lasting action of the carbonic acid does not occur. Finally,- it has been proposed to allow the hot gases coming from ime-kilns or the like to act directly upon'tlie blocks. This process is undesirable because the evaporation of the moisture from the blocks cannot be properly regulated, be cause of the changeable composition and tem erature of the kilngases-,;;as they 'are pro need during the, activity of the kiln. The use of hotlime-kiln-gases produces blocks that are soft and of little soiidity.

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The reason for this is to be found .particu-.

larly in thefact that the evaporation oi the Water out of the blocks proceeds too rapidly if the operation is conducted at a temperature much higher than the boilingpmnt of Water, that is, over, say, 110 The stones thus become too dry, and a large part of' the hydrate of lime contained in the biocks'is not subjected to the action of the carbonic acid. be avoided and very solid blocks obtained if the carbonic acid which is used for the treatment of the same be kept at a temperaturc of from 35 to110 C. and sufficiently free from'humidity that at the same time it exerts drying function, that is it takes up moisture. In this manner Without employing pressure and gases of high percentage and without drying the block beforehand, a thorough conversion of the lime into carbonate can be effected in a short time.

To carry out the process, use may be made of the gases containing carbonic acid, which come from lime kilns, boiler-furnaces, etc. These gases must be cooled to-the designated temperatures and the moisture contained in All these disadvantages can them eliminated .ina suitable manner, so as i to render them capable of taking-Yup moisture from the blocks;

The temperature of the gases used in the treatment must be regulated according to the constitution of the blocks treated, es pecially with reference to their porosity and the amount of hydrate of lime contained, as Well as the purity of the carbonic acid gas. Where the blocks are solid and rich in hydrate of lime, or where the carbonic acid is concentrated, higher temperatures are taken. It is of s)ecial importance in the process however t at the designated maximum temperature be not exceeded. EX- periments have shown that at a temperature. above about 110 C. the carbonic acid acts but incompletely, the hyrdate of lime drying in part and in this condition resisting the action of the carbonic acid.

The blocks to be treated may consist of hydrate of lime or of a mixture of hydrate of lime With calcium carbonate or magnesiumcarbonate, such as limestone, dolomite, magnesite or the like, in combination under certain circumstances with coloring-matters,

miner filling substances, etc. B by? (irate of lime is meant slaked burne lime er burned snh stances .(such as, for instance, hydraulic lime treated with water), c0nta1n-- mg quick 1im.e, treated with Water.

7 We claim as our invention .b1oeks'c0ntaining hydrate of lime which consists intreating the same'with carbonic acid gas eta temperaturebetween 35 and-110? OJ and capable of taking u rnoisture. y

2. The process -of hardening artificial blccks containing hydrate of lime and suitiable carbonates which "consists in treating the same with carbonic acid gas at a teme'rature between 35-'an d'110 O. and, capa- Ele of taking up moisture.

The process of. hardening artificial 3. The process of hardening artificial blocks containing hydrate oflime and suitable coloring matters; which consists in treat In testimony whereof We have signed our names to this specification, in the presence of two subscribing witnesses.

ERICH SOHWANENBERG; ALBERT RINNE.

Witnesses ALFRED SGHWANENBERG, PAUL K. THOMPSON. 

